I am thinking of the mountain again, and this time, I'm thinking about ants! J So, how about heading back there with me?! Here goes: early summer day, not too hot, everything including the grass, so green, trees decked out in their fullest leaves, heavy swish of the wind through their branches, a plethora of chirping birds. The screen door bangs as a little, young version of you leaves the house to head to the backyard by yourself and visit your ant trail and check on the doings of your ants (yeah, I really was always so nerdy). There is occasional kitchen clatter and chatter from the cabin, but you don’t notice. The mountain was plentiful in carpenter ants, the big black ones, about the size of a grown-up thumbnail. Here’s what you’re wondering, if you’re me: how and why are they wearing a trail in the grass so well that the grass is worn down to dirt, so clear that you can see it from standing. You’d spend some time watching them walk along, enjoying the day, observing the way the ants meet and greet each other with their little antennae as they pass in different directions.
And then the questions would begin. What sort of information they are passing to each other, if anything, and how might they be doing it? How awesome is it that they walk along the same path enough to wear the grass down? And how do they find the path? Do they find it by smell? They don’t have eyes do they? How big is an ant brain? Does an ant have a brain? So, I’m all grown up now, and I still want to look into what was going on here. I realize that even after all this neurobiology training, I still don’t know much about ant brains, after all!
So, I have now done my research and I’ve learned a few neat things. A lot of neat things, actually, but here are some of my favorite bits.
Ants are actually incredibly interesting and the study of ant behavior has applications to neuroscience, engineering, ecosystems, and stock markets (whoah!). As for foraging and trail-making, ants make trails using pheromones. The pheromones, depending on the species of ant, are secreted from a variety of gland locations, including glands on the feet, thorax, anus and abdomen. They even release different pheromones for ‘to’ a food source as opposed to ‘away from’ a food source. Ants will leave a pheromone trail behind them as they are leaving a food source, indicating to other ants that the trail had been successful. As the food source is used up, the ants cease leaving this ‘success’ pheromone behind, and the trail scent slowly dissipates. Carpenter ants can make well-worn trails that they use for years, probably guiding them to an area commonly good for food (perhaps towards our camp, for example).
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| Argentine ant trails - Latty et al., 2011 |
While doing my present-day ant exploration (reading, no ant progressions to follow here in the apartment in Montreal that I’ve found, very grateful for THAT), I also found that ant path-making is an area of current active research. In particular, researchers are interested in the way individual ants find the shortest route to a food source or other location with no central influence. Latty et al. arranged a colony of Argentine ants in separate nests and then recorded and studied how they form paths between the nests. They also wanted to know if the number of individual ants made a difference in the way the ants organized network pathways. Here’s what happened: the ants made networks of paths with lengths that increased to a maximum, and then were trimmed down to a final length. At first, individual ants made redundant paths, but overall, through trial and error, the colony of ants produced more efficient pathways. With more ants in the colony, the networks formed were less precise in the end, and the extra total length traveled per ant increased. With too few ants, no paths were created at all.
This fits in interestingly with something else I found. An ant brain has about 250,000 neurons. A human brain has about 100 billion neurons (of course, this is a bit debatable). Some ant researchers liken an ant colony to a single human brain, where each ant could represent a neuron, all of them signaling to each other in various ways. Together they are accomplishing great feats where one neuron in a brain or one ant in a colony could accomplish so very little.
This is also interesting because the authors compare the ant networking situation with, for one, mammalian vasculature development. It’s funny, because little ant paths and networks really do resemble vascular networks in a visual sense. Just like ants don’t always follow the straightest path from A to B, so endothelial cells (the cells that form the inner lining of blood vessels) do not form blood vessels that make straight lines through the human body. And I remember this from anatomy class: not everyone’s vasculature is the same. And most do not look exactly like those diagrams in the textbooks. It’s all just a bit haphazard, organic. And worthy of a lot more study. Perhaps the same principles that guide an individual ant on its journey to find food, is in some global way related to the workings of neurons in a human brain or the relation of individuals to a stock market. This is cool.
Now, I am only scratching the surface of ant science and am certainly not giving it due justice, but that was fun!! Check out the references if you’d like to know more. There are plenty of ant books out there also.
References:
Delgado J, Sole, R (2000) Self-synchronization and task fulfillment in ant colonies. Journal of Theoretical Biology. 205: 433-441.
Jackson DE, Ratnieks FLW (2006) Communication in ants. Current Biology. 16:570-574.
Latty T, Ramsch K, Ito K, Nakagaki T, Sumpter D, Middendorf M, Beekman M (2011) Structure and formation of ant transportation networks. Journal of the Royal Society Interface. Published online 2 February 2011.
Robinson EJH, Ratnieks FLW, Holcombe M (2008) An agent-based model to investigate the roles of attractive and repellent pheromones in ant decision making during foraging. Journal of Theoretical Biology. 255:250-258.
By the way, I am a big fan of old-school Dave Matthews Band. I hope you will enjoy this video as much as I did!!
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